US1121802A

US1121802A - Method of coating projector-lamps with reflecting-surfaces.

Info

Publication number: US1121802A
Application number: US74137313A
Authority: US
Inventors: Emerson L Clark
Original assignee: Nat Carbon Co
Current assignee: National Carbon Co Inc
Priority date: 1913-01-11
Filing date: 1913-01-11
Publication date: 1914-12-22
Anticipated expiration: 1931-12-22

Description

E. L. CLARK.

METHOD OF COATING PROJECTOR LAMPS WITH RBFLEGTING SURFACES.

APPLICATION FILED JAN. 11, 1913.

1,1 21,802. Patented Dec. 22, 1914;

WITNESSES INVENTOR EMERSON L. CLARK By $1M 4AM ATTORNEY UNITED STA ES Arum OFFICE.

EMERSON-L. CLARK, OF LAKEWOOD, OHIO, ASSIGNOR TO NATIONAL CARBON COMPANY, I

' OF CLEVELAND, OHIO, A CORPORATION OF NEW JERSEY.

METHOD OF COATING PROJECTOR-LAMPS WITH REFLECTING-SUBFAGES. 4

specification of Letters Patent, P ;2 9

Application filed January 11, 1913; Serial No. 741,373.

To all whom it may concern Be it known that I, EMERSON L. CLARK, a citizen of the United States, residing at Lakewood, in the county of Cuyahoga and State of Ohio, have invented a certam new and useful Improvement in -Methods of Coating Projector-Lamps with Reflecting- Surfaces, of which the following is a fu 1, clear, and exact description.

My invention relates to a method for internally coating an incandescent lamp with a highly reflecting surface.

In my application filed October 17th, 1912, Serial No. 726204, for incandescent light for projection apparatus, I have disclosed an improved form of projector lamp of the incandescent' type.

This invention relates to a method of applying the reflecting coating on the interior of the incandescent, lamp there disclosed.

Figure 1 is a more or less diagrammatic representation of means for coating an incandescent lamp with reflecting material.

Fig. 2 is an end view of. the arrangement shown in Fig. 1 with means .for cooling certain parts of the lamp. Fig. 3 shows a modified form of the arrangement for coating the lamp. Fig. 4 illustrates a further modification.

If a source of light be partly surrounded by a difl'used reflecting surface and the remaining area of the surfacebe composed; of a medium pervious to light, all of the light emitted from the source must eventually proceeed through sucharea provided the efliciency of the reflecting surface is 100%. That is, if all the light is reflected back and forth from the reflecting surface and none of it is absorbed, it must be all emitted through the light pervious area. However, a diffused reflecting surface of 100% efliciency is not at present obtainable, so that with the lamp constructedas described, the entire light emitted from the source would not pass out through the window or lightpervious area, but a certain amount would be absorbed. The concentratingeffect produced by such arrangement can be approximately computed as follows: Let I be the mean spherical intensity of the extended source within the reflecting inclosure; let R be the reflecting co-eificient of the reflecting inclosure; let P be the per cent. area which is uncoated with reflecting material; let 1' be the radius of the inclosure (assumed .reflecting property is-thus almost spherical). then'the intensity of the illumination produced at the light-pervious area or window is:

'. If, instead of a diffused reflecting surface,

apolished surface is used so that specular reflection 1s had and the interior surface of means that only that part of the light would finally reach the window that was reflected in the plane of the great circles that intersect it. But even with specular reflection, the intensity of light would be greatly increased at the window. However, in practice, it would be impossible to obtain a bulb with such an exact interior surface that the light rays would continue to be reflected in the plane in which they started. As a matter of fact, the interior surface would conslst of m nute surfaces facing n diverse directions. This would be sufficient'to cause all'light to be eventually reflected through the window so that the light emitted through it would 'follow somewhat approximately the lawof diffused reflection. The interior of the bulb may be made with an irregular surface to cause the light to more closely follow this law. From the law of diffused reflection, it will thus "be seen that a' slight increase in the reflecting co-efflcient makes a -large increase in the light emitted through the window. In my application above referred to, the invention is directed broadly to any form of reflecting medium. I have since found that metallic sodium and potassiumhave very. high reflecting co-efiicients, beingin ;the neighborhood of 99.7. Their perfect. Substitutingt is value inthe equation for diflused reflection, we get an intensification of approximatelyW at the window, assuminga window'of 1% area. As explained above, the metallic surface would not follow exactly the law for difl'used reflection, but would-have a t alue somewhat less than that obtained by it. As stated above, the bulb could be coated with a roughening material or be made with rough and irregular protuberances so as to more closely follow this law. Since sodium or potassium oxidize very readily when in the presence of oxygen, it will be necessary 'to apply the coating with no trace of oxygen. I accomplish this result as follow. 5:

Referring to Fig. 1, the incandescent bulb 1 which may be glass or metal as in my prior application, is connected to a container 2 by means of a tube 3. The container is connected to means for producing a vacuum through pipe 4. The vacuum pump or other means is not shown on the drawing. The container 2 contains the sodium, potassium, or other metal. This container may be a glass tube having restricted

ends

3 and 4 connected to the bulb and pump respectively. After the incandescent filament is placed in the lamp, the air is exhausted through the tube 4 and the latter sealed. The sodium or other metal in the container 2 is then heated by any means, a gas jet 5 being shown for the purpose of illustration. The sodium or other metal is vaporized and passes up into the lamp bulb Where it is condensed on the interior surface. In order to prevent the metal from condensing on the window 6, heat should be applied thereto. The window may be heated in any manner but I have shown a heating coil 7 closely adjacent there to and connected to a source of E. M. F. 8. It is also best to send current through the filament 10 in order to prevent the metal from condensing there. After the metal has condensed on the interior of the bulb, the glass tube 3 is sealed off in the usual manner. The bulb is thus provided with a highly reflecting coating of sodium or other metal with the exclusion of oxygen, and it retains its brilliant surface indefinitely. The lamp, when thus coated with sodium or potassium, furnishes a much more concentrated light than with all other known reflecting coatings. In order to more efficiently coat the interior of the bulb, it will be advisable to cool the parts of the lamp to which the coat is to be applied. In Fig. 2, I have shown such an arrangement. Water or other cooling medium is circulated through

jackets

11, 12, which may be hemispherical. The water jackets are shaped to leave openings for heating coil 7, the connecting plug 13 and the tube 3. With the cooling means shown, the deposit of metal will be more regular and the window will have a sharper contour. If desired, the lamp bulb may be coated while placed in a, draft of cool air to cause the deposit of metal.

In Fig. 3, I have shown a further method of preventing the metal from depositing on a aaeoa the window 6. A disk 14 is. laced in the bulb before it is scaled up. T is disk is of the same size as the window desired, and is coated on one side with some material such as soft varnish or felt to prevent its scratching the reflecting surface after the lamp is complete. Before the sodium or other metal is vaporized, thelamp is turned until the disk 14 slides into the proper position, and then the air is exhausted and the metal vaporized. The metal will condense on the interior of the bulb andon the upper surface of the disk 14 but it will not condense on the window 6 because it is covered by the disk. After the coating process is complete, the lamp is turned so that the disk 14 slides off the window. In this way the interior of the bulb is coated with sodium or other metal, leaving a sharply defined Window entirely free from the coating. The reflecting efficiency of the bulb is not impaired by the disk inasmuch as the upper surface of it is coated with reflecting material. handling and in shipping to prevent the disk from turning over with the reflecting surface downward. In this arrangement, current maybe sent through the filaments to prevent the metal from condensing thereon and the bulb may be cooled as in Fig. 2.

In Fig. 4, I have shown a still. further modification. The lamp here shown is intended for a headlight on automobiles or other carriages. It consists of a body portion 15 having a substantially parabolic shape and a transparent portion or window 16. The window 16 may be sealed on to the body portion 15 in any well known way. The light emitting filament used in this type of lamp consists of a helix of thin tungsten strip or foil coiled flatwise with

leads

17 and 18 as shown. By using the thin strip or foil, I am able to concentrate the light source at the focus. The interior of the body portion 15 is to be coated with sodium or other metal and the window 16 is to be uncoated. As a variation of the method above described, I may use mercury, oil or other liquid to prevent the metal from depositing on the window 16. The liquid may be introduced into the lamp throughtube 19. After the air is exhausted from tube 3, the sodium or other metal in the container 2 is heated and is condensed on the interior of the body portion 15. This body portion may be cooled as previously described. The sodium may be allowed t condense on the mercury if such is used, forming an amalgam therewith. After the coating is applied, the mercury or other liquid is withdrawn through tube 19 and it, as well as tube 3, is sealed. In this way, the sodium is prevented from depositing on the window 16. This form of light may be used very efficiently with dry cells for in- Of course,.care should be used in stance. In this modi'fication;- '.,tlie= mercury fact that sodium and potassiiifni havefveryhigh reflecting co-eflicients, but I :b'elieve I am the first to disclose the method-described for applying coatings of such; material to the interior of incandescent lamps.

Having described my inventiomf-what I:-

claim is:

1. The process of coating a bulb with a reflecting surface which consists in freeing the interior of oxidizing gas, heating a supply of the coating material and causing the vapor thereof to condense on the interior surface of the bulb.

2. The process of coating a bulb-with a reflecting surface which consists in freeing the interior of oxidizing gas, heatinga-n external supply of the coating material and causing the vapor thereof to condense 0n the interior surface of the bulb.

3. The process of coating a bulb with a reflecting surface, which consists in freeing the interior of oxidizing gas, leading a supply of vapor into the interior and causing it to condense on the greater part of the interior surface while preventing it from depositing on the remaining surface.

4. The process of coating a-bulb' with a reflecting surface which consists. infreeing the interior of oxidizing gas, heating a portion of the bulb, heating a supply of the coating material and causing the vapor thereof to condense on the interior -'surface of said unheated portion of the 5. The process of coating a bulb with a reflecting surface, which consists in freeing the interior of oxidizing gas, heating a portion of the bulb, cooling the remaining portion and heating a supply of coating material so that the vapor thereof will condense on the interior surface of saidcool of the bulb.

6. The process of making a bulb with reflecting surface whichv consists in forming the .bulb, roughening the interior surface, freeing the interior of oxidizing gas, and causing a vapor to condense on the interior surface. i

7. The process of making an incandescent lamp which consists in forming the bulb, adding the filament, exhausting, the interior, heating the filament, and a portion of the bulb andcausing a vapor to condense on the interior surface of the unheated portion.

8'. The process of making an incandescent lamp which consists in forming the bulb with" a roughened interior surface, adding the filament, exhausting the interior, heating the filament and a portion of the bulb, and causing a vapor to condense on the in-. terior surface of the unheated portion of the bulb.

9. The process of making an incandescent lamp which consists in forming the bulb, roughening a portion of the interior surface, adding the filament exhausting the interior, heating the filament and the non-roughened portion of the bulb and causing a vapor to condense on the said roughened surface.

10. The process of coating a bulb with a reflecting surface which consists in freeing the interior-of oxidizing gas, placing a mov able cover over a portion of the interior surface heatinga supply of the coating material and causingit to condense on the interior surface of the uncovered portion of the bulb. I 1 M In testimonywhereof, I hereunto aflix my signature in the presence ofwitnesses.

EMERSON L. CLARK.

Witnesses:

IRA J. AnA'Ms, H. G. GROVER.

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